1. The behaviour of various types of cortical bone graft has been studied in rabbits by histological and injection techniques.

2. The results suggest that penetration of the graft by blood vessels plays an important part in the incorporation of autogenous and homogenous grafts.

3. Autogenous and homogenous grafts are both incorporated–the latter more slowly than the former–but heterogenous grafts are rejected. The reasons for this rejection are discussed.